Until the days end, under the day's 24 hours there will be very small eggs spread around mostly trees in Dun Morogh, Elwynn Forest, Teldrassil, Azuremyst Isle for Alliance and Mulgore, Durutar and Tirisfal Glades and eversong woods.
Here is some info about the event:
Noblegarden - WoWWiki - Your guide to the World of Warcraft
So in these eggs you find mostly candy, but sometimes you can find very rare dresses which EASILY sells for hundreds and hundreds of gold or even thousands and thousands of gold since they're very rare and can only be find under 24 hours per year and very common that RP:er wants them!
The two types of dresses you are looking for is [Easter Dress] and [Elegant Dress]
1 more thing, the candy, save it, no duration time set! You can have it for ever and it gives stats so you can give it to twinks since it has no level requirement.